Hi going by past puffer experiances if a puffer is not yet secure in his surroundings it will not fan out his tail. IMO totally normal for a puffer in new surroundings.
i have a orange-tail fiji puffer and they are a pygmy puffer like the valentini puffer.i have had mine for about 3 years and i think through those 3 years of having him i have only seen him open his tail about 10 times and every time it happened i was doing a water change and he was swimming the glass. i think that this is totally normal.from what i have read is that they only open thier tail when stressed or scared. dont get so scared its normal.btw have you seen him open it at specific times such as doing a water change or feeding?
I have a blue spotted puffer and he doesn't really open hs tail unless he has too. I tried to put a valentini puffer with him and he did it a lot, had to bring the val. back to the store the next day. Knew it was a 50/50 shot.